optical zoom vs honeycom zoom

[Michael J. Hußmann]

This is actually a good example for the effect of great distances.
Suppose an image shot with a telephoto lens shows two soccer
players that are 10 meters apart -- but as the distance to the
camera is, let's say, 100 meters for the first player and 110
meters for the second, both will be about the same apparent size,
and in the absence of any other depth clues, they could just as
well be only 1 meter apart, for all we know. If, on the other hand,
the distance between the first player and the camera was just 1
meters, the second player would be twice as far (instead 1.1 times
as far as in the first case), so (a) the second player would seem
to be much smaller than the first, and (b) the depth of field might
not suffice to include both.

Oh my, evidently I got confused by my own example -- if the two players are still 10 meters apart, the second will of course be 11 times (not twice) as far as the first.

• Michael--------------------------------------------------------------- http://www.michael-hussmann.de

 

[Michael J. Hußmann]

I have always
read that 90 mm was the focal length that gives the perspective the
closest to human eye perception

It isn't as simple as that -- the human eye is nothing like any photographic lens. I have read that a 35 mm lens gave the best match to our field of vision, which is true in a sense, while it's also true that, just as you said, a telephoto lens more closely captures the essential features of human vision.

What we perceive to be our field of vision resembles that of 35 mm lens, give or take a few millimeters, but at any given time, the actual field of high resolution vision is just a few degrees of angle across. Controlled by the brain, our eyes scan a large area, corresponding to a wide angle lens, but the images we believe we see are actually composed of lots of very small high resolution images, such as we would get from a telephoto lens. Our peripheral vision is good at detecting change and motion (prompting the brain to focus our eyes where the change was detected), but is a complete failure when it comes to capturing any detail. The evolutionary advantages of such a system of vision are obvious: we can make out quite a lot of detail in far away objects, but still react quickly if something potentially dangerous is stalking us from a direction we aren't currently looking at.

In other words, human eyes are both wide angle and a tele lenses, and thus no conceivable camera will ever capture what the eyes see -- or rather, what our brain sees.

• Michael--------------------------------------------------------------- http://www.michael-hussmann.de

 

[Anand67599]

I have always
read that 90 mm was the focal length that gives the perspective the
closest to human eye perception

It isn't as simple as that -- the human eye is nothing like any
photographic lens. I have read that a 35 mm lens gave the best
match to our field of vision, which is true in a sense, while it's
also true that, just as you said, a telephoto lens more closely
captures the essential features of human vision.

Here is my bit of theory

Human eye sees 55 degrees, and thats called 'normal' perspective. a 50mm lens on 35 mm format do the same, thats why portraits are preffered with that setting. indeed human eyes do great other things like detail focus only on interest) human eye has lesser focal length (bents rays severely) on smaller chip(ratina). so you see focal length is not related to perspective. but equivalent focal lenght (f plus format size combined) that matters. otherwise we always would have fisheye type look in all digicam pictures. ofcourse thats not the case.

however central area of the focal plane is sweat spot used by smaller ccd format and hence more DOF(on same eqv. focal length).

In perspective, the subject distance does matter, but not alone. Law of optics needs both subject distance and focal length to form place of image as well as relative lateral(i would invite confusion if i donot use this word, i guess) magnification(for perspective.)

A normal vindication of my 'perspective' would be viewing different (eqv) focal lenght photo with subject distance and angle possibly same.

another perspective to look at this is if digicam lens are to be used to form image on 35mm, it has to cover greater area with edges heavily distorted. thats why we call it 'perspective' as it shows human eyes look ('normal' ) different than 'fish-eye'.

What we perceive to be our field of vision resembles that of 35 mm
lens, give or take a few millimeters, but at any given time, the
actual field of high resolution vision is just a few degrees of
angle across. Controlled by the brain, our eyes scan a large area,
corresponding to a wide angle lens, but the images we believe we
see are actually composed of lots of very small high resolution
images, such as we would get from a telephoto lens. Our peripheral
vision is good at detecting change and motion (prompting the brain
to focus our eyes where the change was detected), but is a complete
failure when it comes to capturing any detail. The evolutionary
advantages of such a system of vision are obvious: we can make out
quite a lot of detail in far away objects, but still react quickly
if something potentially dangerous is stalking us from a direction
we aren't currently looking at.

In other words, human eyes are both wide angle and a tele lenses,
and thus no conceivable camera will ever capture what the eyes see
-- or rather, what our brain sees.

• Michael

--
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http://www.michael-hussmann.de